Urinary and Endocrine Systems Review

Comprehensive vocabulary flashcards covering renal anatomy, nephron physiology, urine formation, and endocrine regulatory mechanisms.

Kidneys function

filter blood and form urine.

Ureters function

transport urine from the kidneys to the urinary bladder.

Urinary Bladder function

store urine

Urethra

eliminate urine from the body

Renin

An enzyme/hormone released by the kidneys that functions to increase blood pressure when low blood pressure is detected.

Renal Hilum

The medial indentation of the kidney serving as the entry and exit point for blood vessels, nerves, and the ureter.

Fibrous Capsule

A dense irregular connective tissue layer directly surrounding the kidney that protects it and maintains its shape.

Perinephric Fat (Adipose Capsule)

A layer of adipose tissue surrounding the fibrous capsule that cushions and supports the kidney.

Renal Fascia

A layer of dense irregular connective tissue that anchors and stabilizes the kidney to surrounding structures.

Renal Ptosis (Nephroptosis)

Abnormal downward displacement of a kidney, occurring more often on the right and in women, which can be caused by a lack of supporting adipose tissue and may kink the ureter.

Hydronephrosis

Dilation of the renal pelvis caused by urine backing up, often due to a kinked ureter.

Renal Columns

Extensions of the renal cortex that project inward into the renal medulla to divide it into renal pyramids.

Renal Pyramids

Conical triangular structures that compose most of the renal medulla, with their broad base at the corticomedullary junction.

Renal Papillae

The medial apex or tip of each renal pyramid that empties urine into a minor calyx.

Nephron

The functional unit of the kidney that filters blood and modifies filtrate to form urine, consisting of a renal corpuscle and a renal tubule.

Renal Corpuscle

The site where blood filtration begins in the nephron, consisting of the glomerulus and the glomerular (Bowman's) capsule.

Proximal Convoluted Tubule (PCT)

The segment of the renal tubule lined by simple cuboidal epithelium with dense microvilli (brush border) and abundant mitochondria; responsible for bulk reabsorption of filtered nutrients, water, and ions.

Descending Limb of Nephron Loop

The nephron loop section with high water permeability and low solute permeability, causing water to leave by osmosis and concentrating the tubular filtrate.

Ascending Limb of Nephron Loop

The nephron loop section that is impermeable to water but permeable to solutes, moving solutes out so the filtrate becomes dilute and the medullary interstitium becomes hypertonic.

Distal Convoluted Tubule (DCT)

The tubule segment lined by simple cuboidal epithelium without a prominent brush border that fine-tunes filtrate by reabsorbing $Na^+$, $Cl^-$, and $Ca^{2+}$ (under PTH regulation).

Principal Cells

Collecting duct cells that respond to ADH to increase water reabsorption and to aldosterone to increase $Na^+$ reabsorption and $K^+$ secretion.

Intercalated Cells

Specialized cells of the collecting duct that regulate acid-base balance by adjusting the secretion and reabsorption of $H^+$ and $HCO_3^-$.

Cortical Nephrons

Nephrons making up roughly 85% of all nephrons, possessing renal corpuscles in the outer cortex, short loops of Henle, and peritubular capillaries.

Juxtamedullary Nephrons

Nephrons making up roughly 15% of all nephrons, positioned near the corticomedullary junction with long nephron loops and vasa recta that establish the medullary osmotic gradient.

Vasa Recta

Long, straight capillary branches that follow the long nephron loops of juxtamedullary nephrons deep into the medulla.

Juxtaglomerular Apparatus (JGA)

A regulatory structure formed where the DCT contacts the vascular pole of the renal corpuscle, functioning to regulate GFR and blood pressure.

Granular Cells

Modified smooth muscle cells of the afferent arteriole that detect changes in stretch/pressure and release renin when renal blood pressure drops.

Macula Densa

Specialized epithelial cells in the DCT that monitor $NaCl$ concentration in tubular fluid to assess flow/GFR and signal granular cells to adjust renin release.

Podocytes

Specialized epithelial cells forming the visceral layer of the glomerular capsule with pedicels that wrap around capillaries to form filtration slits.

Glomerular Filtration

The bulk flow of water and small dissolved solutes from glomerular blood into the capsular space, driven by blood hydrostatic pressure.

Tubular Reabsorption

The transport of substances from the tubular fluid back into the blood of the peritubular capillaries or vasa recta.

Tubular Secretion

The selective movement of substances from the peritubular capillary blood directly into the tubular fluid for eventual excretion.

Glomerular Hydrostatic Pressure (GHP)

The blood pressure within the glomerular capillaries that pushes water and solutes across the filtration membrane into the capsular space.

Blood Colloid Osmotic Pressure (BCOP)

The osmotic pressure exerted by trapped plasma proteins in glomerular blood that draws fluid back into capillaries, opposing filtration.

Capsular Hydrostatic Pressure (CHP)

The pressure exerted by accumulated filtrate inside the capsular space that pushes back against the capillary wall, opposing filtration.

Glomerular Filtration Rate (GFR)

The total volume of filtrate formed by both kidneys per unit of time, directly related to net filtration pressure (NFP).

Intrinsic Renal Autoregulation

The intrinsic myogenic and feedback mechanisms by which the kidney alters afferent arteriole resistance to maintain steady blood flow and GFR despite systemic pressure fluctuations.

Atrial Natriuretic Peptide (ANP)

A hormone released by cardiac atria in response to stretch that increases GFR and promotes $Na^+$ and water excretion to lower blood volume and blood pressure.

Paracellular Transport

The movement of substances across an epithelium by passing through the tight junctions and intercellular spaces between adjacent cells.

Transcellular Transport

The movement of substances directly through epithelial cells, traversing both the apical (luminal) and basolateral plasma membranes.

Transport Maximum ($T_m$)

The maximum rate at which a substance can be reabsorbed or secreted by renal tubule transport proteins before saturation occurs.

Renal Threshold ($R_t$)

The plasma concentration of a substance at which it exceeds tubular transport capacity and begins spilling into the urine (e.g., $180\,\text{mg/dL}$ for glucose).

Glucosuria

The excretion of glucose in the urine, occurring when blood glucose concentrations exceed the renal threshold and overwhelm carrier proteins.

Aldosterone

A steroid hormone from the adrenal cortex that acts on principal cells to increase $Na^+$ reabsorption and $K^+$ secretion, increasing blood volume and pressure.

Obligatory Water Reabsorption

The passive reabsorption of water following solutes by osmosis that occurs independently of hormonal control, primarily in the PCT and descending limb.

Antidiuretic Hormone (ADH)

A hormone released by the posterior pituitary that inserts aquaporin water channels into collecting duct principal cells, promoting water reabsorption and concentrated urine.

Type A Intercalated Cells

Cells in the collecting duct that respond to acidosis by secreting $H^+$ into the tubular fluid and reabsorbing $HCO_3^-$ into the blood.

Type B Intercalated Cells

Cells in the collecting duct that respond to alkalosis by secreting $HCO_3^-$ into the tubular fluid and reabsorbing $H^+$ into the blood.

Paracrine Signaling

A form of local hormone signaling where chemical messengers diffuse through interstitial fluid to act on nearby target cells.

Autocrine Signaling

A form of local chemical signaling in which a released hormone binds to receptors on and alters the activity of the very same cell that secreted it.

Steroid Hormones

Lipid-soluble hormones synthesized from cholesterol, primarily originating from the adrenal cortex and the gonads.

Amine Hormones

Hormones derived from single amino acids; mostly water-soluble (catecholamines, melatonin), except for lipid-soluble thyroid hormones.

Peptide and Protein Hormones

Water-soluble hormones made of amino acid chains that bind to cell surface receptors; forms the largest hormone classification.

Hormone Response Element (HRE)

A specific sequence of DNA in the nucleus that binds a lipid-soluble hormone-receptor complex to stimulate transcription and mRNA synthesis.

Second Messenger

An intracellular molecule (such as cAMP or $Ca^{2+}$) that relays and amplifies a signal received by a membrane receptor inside the cell.

Up-regulation

An increase in the total number of target-cell receptors in response to chronically low hormone concentrations, increasing sensitivity.

Down-regulation

A decrease in the total number of target-cell receptors in response to elevated hormone concentrations, reducing target tissue sensitivity.

Synergistic Interaction

A hormone interaction where two or more hormones collaborate to produce a greater combined effect than either could individually (e.g., glucagon and epinephrine).

Permissive Interaction

A hormonal interaction where the presence and action of one hormone enables another hormone to exert its full effect.

Antagonistic Interaction

A relationship where two hormones elicit opposing physiological effects on the same target parameter (e.g., insulin and glucagon on blood glucose).

Infundibulum

The slender stalk of tissue connecting the hypothalamus to the pituitary gland.

Anterior Pituitary (Adenohypophysis)

The glandular, hormone-producing component comprising 75% of the pituitary gland, regulated by hypothalamic releasing and inhibiting hormones.

Posterior Pituitary (Neurohypophysis)

The neural component of the pituitary gland (25%) that does not synthesize hormones, but stores and releases ADH and oxytocin.

Insulin-like Growth Factor 1 (IGF-1)

A hormone produced primarily by the liver in response to growth hormone (GH) that mediates indirect tissue growth and protein synthesis.

Follicular Cells

Endocrine cells in the thyroid gland that synthesize and secrete thyroid hormones ($T_3$ and $T_4$) to regulate metabolic rate.

Parafollicular Cells (C Cells)

Endocrine cells of the thyroid gland that produce calcitonin to lower elevated blood calcium levels.

Zona Glomerulosa

The outer zone of the adrenal cortex that produces mineralocorticoids, principally aldosterone, to regulate electrolyte balance.

Zona Fasciculata

The middle and thickest zone of the adrenal cortex that produces glucocorticoids, primarily cortisol and corticosterone.

Zona Reticularis

The innermost layer of the adrenal cortex that synthesizes sex hormones, specifically adrenal androgens.

Cushing Syndrome

A condition resulting from chronically elevated glucocorticoids, causing osteoporosis, muscle weakness, rounded face, and upper back fat redistribution.

Pancreatic Beta Cells

Endocrine cells within pancreatic islets that secrete insulin during the fed state to stimulate glucose uptake and lower blood glucose.

Pancreatic Alpha Cells

Endocrine cells within pancreatic islets that secrete glucagon during fasting to raise blood glucose via glycogenolysis and gluconeogenesis.

Ghrelin

A peptide hormone secreted primarily by the stomach during fasting or prior to meals that stimulates appetite and hunger.

Leptin

A satiety hormone released by adipose tissue that provides long-term signals regarding stored energy to decrease appetite.

Semaglutide

A long-acting synthetic GLP-1 receptor agonist that slows gastric emptying, reduces appetite, and stimulates glucose-dependent insulin release.